Coronary heart disease causes ischemia and reperfusion injury in millions of patients in the United States, leading to myocardial loss and cardiac failure. Ischemic preconditioning (IPC), induced by a brief period of ischemia and reperfusion, generates profound protection against later prolonged ischemia. Our recent study showed that the activity of PTEN (phosphatase and tensin homologue deleted on chromosome ten) is negatively related to the induction and decay of IPC. In this research proposal, we hypothesize that PTEN inactivation plays an important role in IPC cardioprotection. The overall goal of the proposal is to establish a direct relationship between IPC protection and PTEN inactivation. To achieve this goal, we will first determine whether IPC-mediated PTEN inactivation is associated with cardioprotection in well-controlled ischemia models and in p47phox knockout mice with deficient production of reactive oxygen species. We will utilize isolated mouse hearts to investigate the effects of increasing duration of IPC ischemia and deficient production of ROS on PTEN activity. These effects will then be correlated with cardiac functional recovery and infarct size after prolonged ischemia and reperfusion (I/R). Moreover, the signaling pathway p47phox/ROS/PTEN/Akt in IPC will be determined. Second, we will determine whether PTEN knockdown provides constant IPC-like cardioprotection in isolated mouse hearts. We will generate conditional cardiac-specific PTEN knockdown mice and then expose these mouse hearts to I/R. Cardiac functional recovery and infarct size will be measured. The role of PTEN in ROS signaling in IPC will be further defined. Third, we will determine whether IPC decreases PTEN activity and induces cardioprotection in an in-vivo mouse model, and whether PTEN knockdown hearts are highly resistant to I/R in the model. We will determine the effects of IPC on PTEN activity and on cardiac functional recovery and infarct size after I/R in wildtype hearts, and then we will compare PTEN knockdown mice with control mice in myocardial infarct size after I/R. PTEN activity will be correlated with myocardial infarct size. Moreover, we will use p47phox deficient mice and hif-1a deficient mice to determine whether PTEN inactivation is necessary for early and late IPC, respectively. We believe the study will establish a fundamental principal that PTEN inactivation is beneficial to the heart subjected to I/R. Therapeutic agents inhibiting PTEN activity may be developed to reduce myocardial loss. PUBLIC HEALTH RELEVANCE: The research proposal will study the mechanisms of ischemic preconditioning by generating conditional cardiac-specific PTEN knockout mice and determining the effects of PTEN deletion on ischemia-reperfusion injury and ROS signaling.